The present invention relates to (i) a retention assembly that includes a compression element, a flexible substrate, and an article compressed between the compression element and the flexible substrate; (ii) a compression element that is capable of attaching an article to a flexible substrate, and (iii) a method of making an assembly that includes an article retained on a substrate by a compression element.
Devices such as respirators and other articles designed to be worn by a user often rely on elastic straps to secure the devices to the user. In the case of respirators that are designed to filter air breathed by a user, it is desirable that an airtight, or nearly airtight, seal be obtained between the respirator and the wearer""s face. In those devices that use elastic straps, the straps may be provided in the form of braided cotton-elastic bands, rubber bands (for example, natural rubber or polyisoprene), or extruded thermoplastic elastomeric materials (for example, KRATON, available from Shell Oil Company).
Methods of attaching the straps to a respirator vary according to the construction of the straps. For example, braided straps may be stapled to the respirator using conventional metal staples, sewn on the respirator, or inserted into buckles that are located on the respirator. Straps may also be welded directly to the respirator. In this instance, the strap is commonly made of a thermoplastic elastomer. Although stapling and welding are commonplace in the art, both techniques have a variety of drawbacks.
Mechanical stapling of an elastic strap to a respirator or other flexible substrate is a complex operation requiring cutting, forming, driving, and clinching a staple while precisely retaining and locating the strap on the respirator. Mechanical stapling in a continuous motion machine may require that the respirators being stapled be stopped, resulting in reduced throughput. Alternatively, the stapler may match the line speed and move along with the respirator (with zero relative velocity with respect to the respirator). Moving the stapler, however, poses significant problems in equipment design and maintenance due to the mass and size of the stapler. Staples also jam frequently and the jams can be difficult to clear from the machine.
A further drawback of mechanical staples is that different leg lengths are required based on the substrate thickness, with thicker substrates requiring mechanical staples with longer legs and thinner substrates requiring mechanical staples with shorter legs.
Another potential issue with mechanical staples is that the filter media of the respirator is typically punctured by a mechanical staple when that staple is used to attach the strap directly to the respirator dome. The punctures where the staple legs pierce the substrate are potential leak paths which can be a source of concern for some manufacturers and users.
Problems with welding the straps directly to the respirators include a) inconsistent attachment of the straps to the respirator, and b) failure of the bond between the strap and the respirator. In addition, welding the straps directly to the respirator limits the selection of strap materials to thermoplastic elastomers that lack certain properties, e.g., heat resistance, when compared to other materials such as polyisoprene.
The present invention provides (i) a retention assembly that includes a compression element, a flexible substrate, and an article compressed between the compression element and the substrate; (ii) a compression element that is capable of attaching an article to a flexible substrate; and (iii) a method of making an assembly that includes an article retained on a substrate by a compression element. The retention assembly, compression element and method of the present invention provide replacements for, e.g., mechanical staples. The retention assemblies, compression elements and methods are particularly useful for attaching elastic articles to the surfaces of flexible substrates without piercing the substrate. One example of attaching an elastic article to the surface of a flexible substrate is the attachment of an elastic strap to a respirator.
The compression element of the present invention can securely retain an article on the surface of a flexible substrate. It is theorized that the flexible substrate is held taut behind the compression element during and after attachment of the compression element to the substrate. The article is compressed between the compression element and the taut flexible substrate. It should be noted, however, that the present invention is not to be limited by theory, which is offered only to potentially improve understanding of the invention.
In one aspect, the present invention provides a retention assembly that includes a flexible substrate with first and second major surfaces and a compression element located on the first major surface of the substrate. The compression element includes a clamping area on a front face of the compression element and first and second bonding areas on the front face of the compression element. The bonding areas are located on opposite sides of the clamping area and are bonded to the first major surface of the substrate. The assembly further includes at least one article located between the first major surface of the substrate and the clamping area of the compression element, wherein the articles are compressed between the flexible substrate and the clamping area.
In a second aspect, the present invention provides a compression element that includes a body with a front face, a back face, and a clamping area on the front face of the body. The compression element also includes first and second bonding areas located on opposite sides of the clamping area on the front face of the compression element, and each of the bonding areas includes at least one energy director. The compression element further includes first and second channels in the front face of the element body, with the first channel located between the first bonding area and the clamping area and the second channel located between the second bonding area and the clamping area.
In a third aspect, the present invention provides a method of making an assembly that includes an article retained on a flexible substrate. The method includes providing a compression element that has a body including a front face and a back face. The compression element also includes a clamping area on the front face of the body and first and second bonding areas on the front face of the body. The first and second bonding areas are located on first and second sides of the clamping area. The method further includes locating the article on a surface of the flexible substrate, followed by locating the clamping area of the compression element on the article with the first and second bonding areas located on opposite sides of the article. The article is then compressed between the clamping area of the compression element and the flexible substrate while the bonding areas are attached to the flexible substrate. As a result, the compression element is attached to the flexible substrate at the first and second bonding areas and the article is retained between the clamping area and the flexible substrate.
These and other features and advantages of the present invention are described more completely below with respect to various illustrative embodiments of the invention and methods of the invention.
In reference to the invention, the following terms are defined as set forth below:
xe2x80x9cadhesively attachxe2x80x9d means to attach two articles by the use of an adhesive;
xe2x80x9cbondxe2x80x9d and its variations mean attach by any suitable technique including, but not limited to, welding (ultrasonically, chemically, etc.), adhesive attachment, and mechanical interlocking;
xe2x80x9cbonding areaxe2x80x9d means an area on a compression element that is capable of bonding to a flexible substrate;
xe2x80x9cclamping areaxe2x80x9d means an area on a compression element that is capable of clamping an article against a flexible substrate;
xe2x80x9ccompressxe2x80x9d and its variations mean to deform an article by compression from its uncompressed state or shape;
xe2x80x9ccompression elementxe2x80x9d means an article that is bonded to a flexible substrate on either side of an article and includes at least two bonding areas and at least one clamping area;
xe2x80x9celasticxe2x80x9d means a material that is capable of being stretched at least 1.2 times in length in at least one dimension and then is able to substantially recover its original size and shape within one minute after removing the deforming stress;
xe2x80x9cflexible substratexe2x80x9d means a substrate that is not as stiff or rigid as the compression element attached to the substrate (for example, the tension induced in the substrate during attachment of the compression element as described below can be retained after the compressive force is removed);
xe2x80x9cpolymerxe2x80x9d includes homopolymers, copolymers or polymer blends;
xe2x80x9cpolymericxe2x80x9d means including at least one polymer and possibly other ingredients in addition to polymers;
xe2x80x9crespiratorxe2x80x9d means a system or device worn over a person""s breathing passages to prevent contaminants from entering the wearer""s respiratory tract and/or protect other persons or things from exposure to pathogens or other contaminants expelled by the wearer during respiration, including, but not limited to filtering face masks;
xe2x80x9ctextured surfacexe2x80x9d means a surface that is not smooth, e.g., a surface that includes some structure (such as ridges, fish-scale patterns, etc.); a finish (such as a knurl pattern, etc.); or additional components secured on the surface (e.g., particulates, etc.); and
xe2x80x9cweldxe2x80x9d means to attach two articles by melting or fusing.